A new UK study by the Environmental Audit Committee has concluded that passengers in cars and taxis are being exposed to air pollution up to 15 times greater than cyclists and pedestrians on busy city streets.

Part of the problem is that emissions are much higher in the centre of a carriageway, where vehicles suck in dirty air from those in front. Another vital issue is that cabin filters are often ineffective because they are not changed on a regular basis.

A group of five MPs who sit on the Environmental Audit Committee (EAC) carried out an experiment where each was provided with a airborne pollution measurement device linked to a GPS tracker device, by scientists from King’s College London.

The study found on average each person inhaled around 50 million particles per breath while inside a cab in London, around seven times more than the six to seven million particles per breath inhaled while walking around city streets. Persistent inhalation of air pollution and traffic emissions has been linked to lower life expectancy and serious illnesses, including heart disease and cancer.

Ben Barratt, a lecturer and air quality scientist at King’s College, said “When you are in a vehicle, nose to tail, you are right in the middle of the source of the pollution. Vehicles close together suck in each other’s emissions.” Dr Barratt added that often dirty air became trapped in cars and taxis, whereas cyclists and pedestrians had a constant flow of air from all directions.

Research suggests that up to 29,000 premature deaths are caused each year in Britain by pollution, 10 times the number of people killed in road accidents. The biggest concern is tiny pieces of carbon, around 30 times smaller than a human hair, which are so small they can get into the lungs and even enter the bloodstream, passing through major organs, such as the heart and brain.

The main line of defence against this pollution is of course the vehicle cabin filter. However, awareness of their importance and the need to have them changed regularly is often still very limited with both motorists and garages.